“Motor vehicle body” is here understood as meaning not only the complete motor vehicle body but also those large parts of such a body in which the problems described below occur in the same manner.
When the “tempering” of a motor vehicle body is mentioned herein, it is intended to mean the bringing about of a specific temperature of the motor vehicle body that it initially does not possess. It can be a temperature increase or a temperature reduction. “Tempered air” is understood as being air that has the temperature required for the tempering of the motor vehicle body.
A case of the tempering, namely the heating, of motor vehicle bodies that occurs frequently in the automotive industry is the operation of drying the coating of a motor vehicle body, whether the coating be a paint or an adhesive or the like. The following detailed description of the invention is given using the example of such a drier.
When “drying” is mentioned herein, it is intended to mean any operation in which the coating of a motor vehicle body, in particular a paint, can be made to cure, either by expelling solvents or by crosslinking the coating substance.
Known devices of the type mentioned at the beginning that are configured as driers conventionally possess a pressure chamber on both sides of the tempering tunnel, which in this case is referred to as the drying tunnel. The nozzles, which are accommodated in the walls separating the pressure chambers from the drying tunnel, normally have the same construction, in particular the same projection distance, and differ at most in their orientation, that is to say in the direction of projection; this is chosen in each case so that it is aimed at specific surface regions of the motor vehicle body that is to be dried. All the nozzles in effect act only upon the outer surface of the motor vehicle body. If the air streams emerging therefrom also pass through openings into the inside of the motor vehicle body, they have no appreciable effect there owing to their short reach, especially since two such nozzles generally face one another with opposing flow directions and thus mutually compensate for the action in the interior.
Motor vehicle bodies have recently become increasingly more complex in their construction. In particular, they have different masses in different regions. For example, the lowermost region, the sill region or the floor assembly, has a high mass and consequently possesses a considerable heat capacity. Heating of the different regions of the motor vehicle body that is carried out from only one side requires a not inconsiderable time until the heat has penetrated those regions completely. In addition, that time differs locally according to the mass distribution and the distribution of the heat capacities in the region in question. The dwell time of the motor vehicle body that is to be dried in the drier must therefore be adapted to the longest time that is required for drying of the region of the motor vehicle body that is least favourable and has the greatest mass. Not only are the cycle times of the drier increased as a result; overheating can additionally occur in those regions of the motor vehicle body that dry more quickly. This can be particularly disadvantageous where different materials, including heat-sensitive materials, have been used in the motor vehicle body and/or adhesive bonds have been produced.
An object of the present invention is to configure a device of the type mentioned at the beginning in such a manner that shorter cycle times can be achieved.